1. Field of the Invention
The present invention relates generally to audio processing, and more particularly, to a noise suppression processing of an audio signal.
2. Description of Related Art
There are numerous methods for reducing background noise in an adverse audio environment. A stationary noise suppression system suppresses stationary noise by either a fixed or varying amount. A fixed suppression system suppresses stationary or non-stationary noise by a fixed number of dB. The shortcoming of the stationary noise suppressor is that non-stationary noise will not be suppressed, whereas the shortcoming of the fixed suppression system is that it must suppress noise by a conservative level in order to avoid speech distortion at low signal-to-noise ratio (SNR).
Multiple microphone noise suppression algorithms can use an inter-microphone level difference (ILD) cue as a basis for discriminating between the background noise and the target speaker. While ILD is a very strong cue in many situations (especially in close-talk, with spread microphones), it is much less discriminative in others. For example, in far talk mode and for close microphones, the speech and noise ILD overlap to a large extent. Furthermore, even in close-talk mode, problems arise in “off-position” (when the phone is not in the ideal position for which it was calibrated). For these reasons, an ILD-only speech and noise discrimination is not optimal in all situations.
To overcome the shortcomings of the prior art, there is a need for an improved noise suppression system for processing audio signals.